Anti-tip wheel

Abstract

A resilient anti-tip wheel suspension includes a wheel coupled to a first mounting bracket. A second mounting bracket is adapted to be rigidly mounted to a wheelchair. Upper and lower bars each have front and rear ends that are pivotally connected to the second mounting bracket and the first mounting bracket, respectively, so as to form a parallelogram configuration.

What is claimed is:  
     
       1. A resilient anti-tip wheel suspension for a wheelchair comprising: 
       a wheel coupled to a first mounting bracket;  
       a second mounting bracket adapted to be rigidly mounted to a wheelchair; and  
       an upper bar and a lower bar each having front and rear ends pivotally connected to the second and first mounting brackets, respectively, so as to form a parallelogram configuration, the upper and lower bars forming a four-bar system, wherein the upper bar comprises upper longitudinal bars and the lower bar comprises opposing lower longitudinal bars, the opposing upper longitudinal bars being connected together by at least one upper lateral bar, the opposing lower longitudinal bars being connected together by at least one lower lateral bar.  
     
     
       2. A resilient anti-tip wheel suspension for a wheelchair comprising: 
       a wheel coupled to a first mounting bracket;  
       a second mounting bracket adapted to be rigidly mounted to a wheelchair; and  
       an upper bar and a lower bar each having front and rear ends pivotally connected to the second and first mounting brackets, respectively, so as to form a parallelogram configuration, wherein one end of one of the bars is connected to one of the mounting brackets via a torsion elastic pivotal connection.  
     
     
       3. A resilient anti-tip wheel suspension for a wheelchair comprising: 
       a wheel coupled to a first mounting bracket;  
       a second mounting bracket adapted to be rigidly mounted to a wheelchair; and  
       an upper bar and a lower bar each having front and rear ends pivotally connected to the second and first mounting brackets, respectively, so as to form a parallelogram configuration, wherein the front end of the lower bar is connected to the second mounting bracket via a resilient pivotal connection, said resilient pivotal connection being comprised of a cylindrical bore extending laterally through the second mounting bracket, the cylindrical bore being adapted to receive a torsion elastic element.  
     
     
       4. The resilient anti-tip wheel suspension of  claim 3  wherein the torsion elastic element includes a rigid inner sleeve and a rigid outer sleeve defining an annular void therebetween for receiving an elastomeric member. 
     
     
       5. The resilient anti-tip wheel suspension of  claim 4  wherein the elastomeric member is rubber. 
     
     
       6. The resilient anti-tip wheel suspension of  claim 4  wherein the outer sleeve includes an outer surface and a key extending radially from the outer surface, and wherein the cylindrical bore has a key way, the key being engageable with the key way to prevent the torsion elastic element from rotating relative to the second mounting bracket. 
     
     
       7. The resilient anti-tip wheel suspension of  claim 4  wherein the inner sleeve of the torsion elastic element is adapted to matingly engage at least one of the longitudinal bars so as to remain fixed relative thereto. 
     
     
       8. The resilient anti-tip wheel suspension of  claim 7  wherein the resilient pivotal connection further includes a hexagonally shaped pivot pin, the inner sleeve being hexagonally shaped and the longitudinal bar having a hexagonally shaped bore, the hexagonally shaped pivot pin being received by the hexagonally shaped inner sleeve and the hexagonally shaped bore. 
     
     
       9. A resilient anti-tip wheel suspension for a wheelchair comprising: 
       a wheel coupled to a first mounting bracket;  
       a second mounting bracket adapted to be rigidly mounted to a wheelchair;  
       an upper bar and a lower bar each having front and rear ends pivotally connected to the second and first mounting brackets, respectively, so as to form a parallelogram configuration; and  
       a pivotal lockout hook pivotally connected to the second mounting bracket, the pivotal lockout hook including a hook, the hook being displaceable into engagement with a the lower bar.  
     
     
       10. The resilient anti-tip wheel suspension of  claim 9  wherein the lower bar includes two longitudinal bars and a lateral bar extending between the two longitudinal bars, the hook being engageable with the lateral bar. 
     
     
       11. The resilient anti-tip wheel suspension of  claim 9  wherein the pivotal lockout hook includes a pair of laterally spaced longitudinal members forming a yoke for receiving a lower end of the second mounting bracket. 
     
     
       12. The resilient anti-tip wheel suspension of  claim 11  further including a bore passing through a lower end of the second mounting bracket, the laterally spaced longitudinal members having a bore passing therethrough and being adapted to coalign with the bore passing through a lower end of the second mounting bracket, the aligned bores being adapted to receive a pivot pin for pivotally coupling the pivotal lockout hook to the lower end of the second mounting bracket. 
     
     
       13. The resilient anti-tip wheel suspension of  claim 9  wherein the pivotal lockout hook is adapted to be manually controlled. 
     
     
       14. The resilient anti-tip wheel suspension of  claim 9  wherein the pivotal lockout hook is adapted to be controlled automatically in response to an angular disposition of a reclining wheelchair seat back. 
     
     
       15. A resilient anti-tip wheel suspension for a wheelchair comprising: 
       a caster assembly including a caster housing and a first mounting bracket, the housing pivotally supporting a rotatable wheel;  
       a four-bar suspension system including two upper bars and two lower bars, the upper bars being connected together by an upper lateral bar and forming front and rear upper yokes, the lower bars being connected together by a lower lateral bar and forming front and rear lower yokes, the first mounting bracket being pivotally connected to the upper and lower rear yokes; and  
       a second mounting bracket including a housing, the second mounting bracket being adapted to be mounted to a wheelchair, the second mounting bracket housing including a cylindrical bore, a torsion elastic element being adapted to be received by the bore, the second mounting bracket housing being pivotally connected to the upper and lower front yokes so as to form a parallelogram structure, the second mounting bracket housing being pivotally connected to the lower front yoke via the torsion elastic element.  
     
     
       16. The resilient anti-tip wheel suspension of  claim 15  further including a pivotal lockout hook pivotally connected to a lower end of the second mounting bracket housing, the pivotal lockout hook including a hook, the hook being displaceable into engagement with the lower lateral bar. 
     
     
       17. The resilient anti-tip wheel suspension of  claim 16  wherein the pivotal lockout hook is adapted to be controlled automatically in response to an angular disposition of a reclining wheelchair seat back.